Where did all the stink bugs go?

This Thursday, April 14, 2011 file photo shows a brown marmorated stink bug at a Penn State research station in Biglerville. The bug at that time was causing millions of dollars in damages to crops in the mid-Atlantic region. (AP Photo/Matt Rourke, File)

Area farmers say they’re happy that stink bugs — the smelly brown insect that feeds on crops — seem to be waning, although they don’t quite know why.

“This past year, we’ve seen almost none,” said Jeannette Grabe of Canter Hill Farm in Malvern. “I have no clue. I don’t know where they’ve been.”

The mystery of the vanishing stink bugs is puzzling entomologists, too.

“I’m not quite sure why the numbers are down,” said Timothy Abbey, Penn State Extension entomologist.

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The bugs, officially known as the brown mamorated stink bug, were first reported in Allentown in September 1998. As of September 2010, the bug has been recorded in 37 counties in Pennsylvania.

According to a fact sheet from Penn State’s entomology department, stink bugs feed on a variety of plants that include peaches, figs, mulberries, citrus fruits and persimmons. They’ve also been found feeding on blackberries, sweet corn, field corn and soybeans.

While other states, such as Nevada and Maryland, are reporting major problems with the invading insects this year, locals seem to be having fewer problems with stink bugs.

Lewis Barnard, owner of Barnard Orchard Greenhouses in Kennett Square, said that in 2011 the bugs caused damage to 30 percent of the orchard’s peaches and 50 percent of its apples.

“Two years ago, we had a big issue,” Barnard said. “This year the fruit hasn’t shown any damage.”

Vegetable farms also said they have noticed a drop in stink bugs. Pete Flynn of Pete’s Produce in West Chester said that while they’ve had an increase of other pests, like spider mites, stink bugs seem to be missing.

“They’re not so bad right now,” said Flynn. “They really kind of scared the heck out of us a couple years ago, but this year it’s not a big deal.”

As to why the reduced number, Abbey said he was unsure about the exact reason. Some say weather and an increased use of effective pesticides may be causes for the decline.

Barnard noted that his orchard has found more efficient ways to use insecticides to combat stink bugs.

“We didn’t increase the number of sprays this year, instead, we are using something that is going to work,” Barnard said. “That first year we had stink bugs, we weren’t doing that. We were using the softest spray material we could, and it didn’t do the job.”

“People should know that sometimes fruit does have damage, and we’re trying to do our best to not overtreat, but to instead manage the problem,” he added.

Abbey said that while the stink bug population might not be as high right now as it has been before, the bugs continue to reproduce throughout the summer, and another generation of the bugs might show up in late August or September.

“This year, so far, occasionally I see a peach with one, but it’s very minimal,” Barnard said. “Having said that, they breed throughout the summer. When we get to apple harvest season, we will see what that turns into.”

Abbey added that while more stink bugs could pop up between now and September, most growers would likely notice if there was a serious issue at this point in the season.

As for now, the mystery of the stink bugs remains unsolved.

“A few years ago, there seemed to be a massive number,” said Abbey. “In the summer, we’d see them and then by fall, there would be a ton of them. The last two years, their numbers seem to be down, but I have yet to hear a specific reason why.”